1. Field of the Invention
The present invention relates to a method for beneficiating phosphate-bearing materials and is particularly directed to an improved method for separating dolomitic impurities from phosphate ores.
2. Prior Art
Phosphate bearing ores occur widely throughout the world, including central Florida, Idaho, Montana, Wyoming and Utah. All such ores contain impurities which must be removed in order to increase the phosphate content of the ore and to lessen the environmental impact thereof when used in fertilizer materials to enrich farmlands and increase crop yields and to enable the use thereof in the manufacture of phosphoric acid.
Most phosphate bearing ores particularly those found in central Florida and, most particularly, those found in the lower areas of such deposits contain alkaline earth metal carbonate mineral (i.e., dolomite) impurities. Dolomitic impurities are particularly disadvantageous in the manufacture of phosphoric acid since they contribute to substantial increases in the viscosity of the "green acid" prepared in the first stages of acid production.
A variety of flotation and heavy media separation techniques have been proposed in the past to separate dolomitic impurities from phosphate ores. Typical of such methods are those described in U.S. Pat. Nos. 2,293,640; 3,259,242; 3,462,016; 3,462,017; 3,807,556; 4,144,969; 4,189,103; 4,364,824 and 4,372,843.
In order to achieve sufficiently high concentration of phosphate fractions and to satisfactorily eliminate sufficient amounts of dolomitic impurities to enable the efficient use of such fractions in the preparation of phosphoric acid, it has been necessary in the past to employ expensive flotation reagents, multiple step procedures and elaborate systems, all of which contribute significantly to the overall cost of the prior art separation methods.
It is an object of the present invention to provide an improved method for beneficiating phosphate bearing ores containing dolomitic impurities.